Two-Dimensional Crystallization of Biological Macromolecules - Molecules: Nucleation, Aggregation and Crystallization - page 95

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Two-Dimensional Crystallization
of Biological Macromolecules

Hans Hebert*

Biological macromolecules can be arranged periodically in single layers as two-
dimensional (2D) crystals. This enables crystallographic structure analysis using
transmission electron microscopy. Periodic repeat of a large number of unit cells
contributes to significant information in images or diffraction patterns from
unstained specimens. Structural details at a resolution of a few Ångströms in all
directions can be obtained. Such three-dimensional maps are used for building
atomic models. The techniques have been used to determine structure and func-
tion relationships for membrane proteins. The dense packing obtained in 2D
crystals can also be used for constructing devices at the molecular level.

Keywords: 2D crystallization; membrane proteins; crystals.

Introduction

In 1975 Richard Henderson and Nigel Unwin showed that three-dimen-
sional (3D) structural information in the subnanometer region could be
obtained from unstained protein molecules arranged periodically in a
plane as a two-dimensional (2D) crystal (Henderson, Unwin, 1975). Their
results spurred a great deal of effort in many laboratories to produce 2D
crystals for structural studies. Since then several membrane proteins have
been characterized, several at high resolution, with the use of this strategy.

*Karolinska Institutet, Department of Biosciences and Nutrition and Royal Institute of
Technology, School of Technology and Health, Novum, S-141 57 Huddinge, Sweden.
E-mail: [e-mail].